"I've got a lot of surprises for you tonight," Justin Bieber promised fans Tuesday (Aug. 31) at the start of his sold-out, first-ever headlining concert at Madison Square Garden -- and he wasn't kidding. Everyone from Miley Cyrus, Sean Kingston and Jaden Smith to Boyz II Men, Usher and Ludacris joined the 16-year-old pop phenom onstage for a show frantically paced and carefully calibrated to hold the attention of his tween army.

The surplus of guest appearances was no coincidence. Bieber's MSG show was being taped for his upcoming 3-D biopic ("Everyone in this audience is gonna be in my movie!" he told the crowd), and the singer appropriately pulled out all the stops for the cameras. After kicking off his under two-hour set with the Cardigans-inspired "Love Me" -- from his debut album "My World," released less than one year ago -- Bieber introduced Boyz II Men to assist him on new single "U Smile," which this week marks his highest debut to date on Billboard's Pop Songs chart (No. 33). Bieber then returned the favor by introducing a new generation to Boyz II Men's hit ballad "On Bended Knee," singing it with the group a cappella. "These people are the ones who made me want to start singing," he explained, dedicating the song to his mother.

Much of the show served as a window into Bieber's childhood, or a literal projection of his destined-for-success narrative. As he walked offstage for a quick outfit change after singing "Stuck in the Moment," a YouTube-style montage on the JumboTron revealed baby pictures and home video footage of Bieber strumming the guitar as a toddler. Soon, it showed a pre-teen-and-up Bieber tackling Justin Timberlake songs with ease, hobnobbing with Diddy and hitting the studio with Usher. The footage ended with a simple message typed in Comic Sans -- "I love you all :)," met with a rousing chorus of cheers.

In case fans had any doubts, Bieber made that message crystal clear by occupying a seat in a silver, heart-shaped structure that lifted him over the audience. From that lofty height, he performed a medley of his own "Favorite Girl" and Kanye West's "Heartless" on acoustic guitar. "This is for you, Kanye," Bieber said to the rapper, who wasn't in attendance but recently remixed one of Bieber's most adult-leaning R&B tracks, "Runaway Love," with Raekwon of Wu Tang Clan.

"When I was in my heart and I was flying above you guys, I feel like I saw that one special girl," Bieber said once he'd touched back down onstage. He launched into a yearning rendition of "One Less Lonely Girl" as a shaken, petite blonde was plucked from the audience to receive a bunch of red roses -- and a few flirtatious caresses -- from her musical crush.

Just a few days earlier, Bieber postponed a show due to illness, and he was cleared at the last minute to perform on Tuesday. If the young star was still feeling under the weather, though, he didn't show it, instead upping his energy level as one more guest after another joined him onstage. Fans responded in kind, elevating their already high-decibel shrieks to a fever pitch when Usher appeared to duet with Bieber on the ecstatic "Somebody to Love." The elder star and his protege nimbly recreated their student-teacher dynamic from the song's music video, trading dance moves and verses and ending with a giant bear hug. Even the ballad "Overboard" supplied kinetic energy, as a glamorously coiffed Miley Cyrus stood in for Bieber's usual duet partner, opening act and Island Records labelmate Jessica Jarrell.

"There's gonna be times in your life when people tell you you can't sell out Madison Square Garden," Bieber said after Cyrus exited, outlining a highly unlikely scenario for any 16-year-old but himself. "This is what I tell them." As the hip-hop-lite beat of "Karate Kid" soundtrack anthem "Never Say Never" kicked in, Bieber was joined by actual karate kids and 11-year-old sprite Jaden Smith (the movie's star), who unleashed guest rhymes and dance moves with the kind of jarring poise that can only be inherited (his father is Hollywood actor and rapper Will Smith).

Opening act Sean Kingston joined Bieber for their ode to trifling teen girls, "Eenie Meenie," before Bieber slowed down at sat at the piano to perform "Down to Earth," a vulnerable ballad about his parents' divorce when he was a young child. As he waved goodbye and left, it was clear fans wouldn't be satisfied with such a down-tempo closer, and so Bieber soon returned with a more fitting conclusion: "Baby," his generation-spanning "My World 2.0" lead single and biggest hit yet. Donning a red-and-white varsity jacket, Ludacris joined him onstage to deliver his guest verse and help Bieber shower the crowd with celebratory confetti and streamers. For one night only in New York, thousands of fans were invited to celebrate Biebermania, and its subject didn't disappoint, providing as much access into a well-connected teen megastar's world as one could possibly offer.